When a battery of a first motor vehicle is flat (no power), it is known to connect a battery from a second vehicle source across the flat battery in order to start the engine of the first vehicle. Such a technique is commonly referred to as jump starting. It is also known that a flat battery may be recharged by connecting a power source such as a battery charger across the flat battery.
When the battery of a motor vehicle is difficult to access or is not located in the engine compartment, but elsewhere in the vehicle, it has become common practice to provide jump start terminals in the engine compartment which can be connected to either a battery of a second vehicle or a battery charger should the battery of the first vehicle go flat. If the second battery or the battery charger is incorrectly connected (that is, the wrong polarity) to the jump start terminals, electrical components in the first vehicle (especially diodes associated with the generator of the first vehicle) may be damaged. Other conditions which cause the jump start terminal to short circuit to ground can also cause damage.
Weber, U.S. Pat. No. 5,230,637, describes what can happen when sparking or a damaged battery are present when jump starting a vehicle.
As the need for energy in motor vehicles increases with the addition of more electrically powered components and systems, vehicle manufacturers are contemplating higher voltage electrical architectures. The introduction of higher voltage systems increases the probability that someone will try to jump start or recharge a conventional 12 volt battery from a source that has a higher voltage. This situation can damage the battery or electrical components in the vehicle. Use of higher voltages also increases other risks resulting from sparking.
The prior art includes inventions that address the problem of reverse polarity connections when jump starting a battery. Weber '637 provides for jumper cables with reverse polarity protection. Another example of a jump start protection system is described in Alksnat, et al., U.S. Pat. No. 6,211,577. Alksnat '577 utilizes a jump start circuit, a switch, a logic circuit, and a timer circuit. The '577 patent monitors polarity differences across the jump start terminals and closes the jump start circuit switch if polarities match. A timer circuit is used to open the switch after a predetermined period of time. A manual push button is provided to enable the operator to manually close the jump start circuit switch when a second vehicle is used for jump starting.
In the prior art, in order to provide jump start or reverse polarity connection protection it is necessary that either special jump start cables are used or additional operator actions are performed over and above the traditional jump start method.